Questions about reboot and sync in ddb

[Sverre Froyen <sverre%viewmark.com@localhost>]

Hi,

While debugging a drm problem where the ddb dialog is hidden behind 
an Xwindows screen, I find that reboot and sync are very fickle commands.

With no mounted file systems, they seem to operate as expected. 
With root mounted, sync will frequently fail to complete a dump (or even start 
one) especially if root is dirty. I also notice a difference between the 
ahcisata and the piixide drivers, with ahcisata much more likely to fail.

I multiuser mode even a reboot may fail. Typing "sync" a few times before the 
system crashes and using the  piixide driver improve the odds of a successful 
reboot in ddb.

This is on current amd64.

Are these know issues? Should I try to track them down?

Finally, I notice the following output after I type reboot:

db{0}> reboot
syncing disks... iwn0: fatal firmware error
firmware error log:
  error type      = "NMI_INTERRUPT_WDG" (0x00000004)
  program counter = 0x000006E4
  source line     = 0x00000126
  error data      = 0x0000000203630000
  branch link     = 0x000005AA000006E8
  interrupt link  = 0x000008B2000089A2
...

Since I am partially responsible for the current iwn driver, I wonder if it is 
missing some code that would keep it from running during the reboot?

Thanks,
Sverre